Figure 4.

Pathogenesis of SARS-CoV-2. By inhibiting the ACE2’s function, SARS-CoV-2 could cause the injury of the lung. ACE2 plays an important role in the renin-angiotensin system (RAS). Firstly, renin converts angiotensinogen into angiotensin I (AngI), and then AngI is converted into AngII under the ACE2’s action. ACE2 down-regulates the AngI’s and Ang II’s levels. Then, the Ang II type I (AT1) receptors are bound by Ang II, causing lung injury, which includes acute lung injury, pulmonary fibrosis, and pulmonary hypertension. At the same time, Ang II can directly induce rapid growth or proliferation of pulmonary artery smooth muscle cells through AT1, thereby causing pulmonary hypertension. Besides the intestines and lungs, the heart, kidney, esophagus, bladder, ileum, testis, and adipose tissue also could express ACE2, and its level is higher than that of the lung. In addition, tumor tissues have high ACE2 expression, making cancer patients more vulnerable than others.